S. Atieh EN-MME Manufacturing R&D for SPL β =1 cavities at CERN on behalf of the SPL cavities mechanical design and manufacturing team

EBW updates S. Atieh EN-MME EB welding DESY & others: Vacuum: 5x10 -6 mbar Pumping time: ca. 20 min 2 Cryogenic - Pumps: ca. 2  l/s Iris welds (inside) equatorial welds (outside) DESY & others: Vacuum: 5x10 -6 mbar Pumping time: ca. 20 min 2 Cryogenic - Pumps: ca. 2  l/s Iris welds (inside) equatorial welds (outside) CERN late 80’s (50 m of EB welds for LEP Nb cavities) : Vacuum: 5x10 -5 mbar Pumping time: ca. 20 min Oil diffusion – Pump Special vacuum chamber Internal gun for equatorial welds CERN 2011 Vacuum: 5x10 -4 mbar Pumping time: ca. 20 min Oil diffusion – Pump Special vacuum chamber Internal gun for iris welds f(iris opening) External gun for equatorial welds CERN 2012 (8 m EB welds for 1 x β=1 SPL cavity): New EB welding machine 2012 at CERN Chamber (6x1.4x1.4 m 3 ), P down to mbar Electron beam generator with fast beam deflection (200 kHz) Electron-optical viewing system No internal gun (for SPL) but deflection system could be an alternative.

Working Pressure vs. RRR S. Atieh EN-MME EB welding The RRR degradation can take place in the welding seam itself, but also in the HAZ (courtesy of W. Singer)

Cavity interfaces S. Atieh EN-MME EB welding (courtesy of W. Singer) Niobium to titanium grade 5 (Ti6Al4V) EB welding successfully tested before and after heat treatment at 800 °C Formal qualification according to ISO is ongoing Mechanical testing at low temperature is ongoing

Nb / Ti V S. Atieh EN-MME EB welding Before HTAfter HT UTS (MPa)152.7 ± ± 2.2 Elongation at break (%)24.8 ± ± 0.1

Cavity interfaces S. Atieh EN-MME EB welding (courtesy of W. Singer) Niobium to titanium grade 5 (Ti6Al4V) is not SPL nominal configuration Nb / SS 316 LN is requested Nb / SS 316 LN can not be joined done by fusion welding Iron rich compound (intermetallics)

Stainless steel interfaces S. Atieh EN-MME Brazing (courtesy of W. Singer) Brazing Nb / SS 316 LN is a key technology Developed at CERN in the Difference in expansion of Nb/SS Nb tube fitted to SS flange Clearance ≤ 20 µm SS plug to expand the Nb Pure Cu filler metal Brazing temperature 1100°C, ∆ time << P< mbar

Stainless steel interfaces S. Atieh EN-MME Brazing (courtesy of W. Singer) Ultrasonic examination Leak testThermal shock liquid N2 (x5)Ultrasonic examinationLeak testElectro-polishingHT ( 600°C/24h)Electro-polishingLeak testUltrasonic examinationThermal shock liquid N2 (x5)Ultrasonic examinationLeak testShear testLeak testUltrasonic examinationAssembly testMacroscopic examinationSEM assessment

Stainless steel interfaces S. Atieh EN-MME EB welding INTERMETALLICS NumberHV

Cold gas dynamic spray S. Atieh EN-MME Thought Solid- state coating deposition method a supersonic gas (N2) jet that propel fine coating powder particles ( 1-50 μm) at very high velocities ( m/s). Advantages: powders are not melted almost absence of oxidation during the process allows materials to be constructed layer upon layer Nb sheets ( t=1 mm,3 mm) with Cu cold spray OBZ GmbH/ Germany

Cold gas dynamic spray S. Atieh EN-MME Thought Tubular Coating Tensile Test (TCT-Test) Micro Flat Tensile Test (MFT-test) Metallurgical characterization H ELMUT S CHMIDT U NIVERSITY University of the Federal Armed Forces Hamburg

? S. Atieh EN-MME Thought Cu substrate Nb coating

Menu for S. Atieh EN-MME Perspective Continue the actual program Weld characterization for Nb cavities: “weld distortion and shrinkage” Explore the new EB welding machine (Nb welds): filler metal, repair etc. Setup the fabrication of a Nb cavity Work on NDT: X-Ray tomography &…

Last slide S. Atieh EN-MME Conclusion A.E. "If at first, the idea is not absurd, then there is no hope for it" Having a critical view to existing solutions “occasionally” could be advantageous. We learned during the fabrication of Cu cavity and will apply many things to the fabrication of Nb cavities. New EB welding machine in Feb. and we will start the machine qualification program for the Nb welds. 5 th Nb cavity will be fabricated at CERN in Key technologies identified and tests are ongoing (manufacturing backup)

S. Atieh EN-MME Thank you for your attention ?

Industrial Cavity Fabrication (DESY) S. Atieh EN-MME

Industrial Cavity Fabrication (DESY) S. Atieh EN-MME

Industrial Cavity Fabrication (DESY) S. Atieh EN-MME

Industrial Cavity Fabrication (DESY) S. Atieh EN-MME

Working Pressure vs. RRR S. Atieh EN-MME Backup W. Singer, 11th SRF Workshop, September 2003

Nb / Ti V S. Atieh EN-MME Backup NbTi6Al4V ρ (Kg/m 3 )8600 – 8700 ( x 1.9)4410 – 4450 (/ 1.9) T m ( o C)2460 – 2470 (+830)1610 – 1660 (-830) K (W/m o C)54 – 57 (x 7.7)7.1 – 7.3 (/ 7.7)

New EBW machine S. Atieh EN-MME Backup